Balanoglossus are dioecious, having separated biologicalsexes and gonads prominent into body cavity (Biocyclopedia, 2012). The male gonads have an orange colour while the females aregrey or green (Mandal, 2012).
Theyreproduce sexually, though the releasing of eggs and sperm into the water (NewWorld Encyclopedia, 2008). Their gonads are situated close to the pharynx sothem can release the gametes through a small pore proximate of the gills slits (Sawaya,1964).
Thefemale lays a great quantity of eggs embedded in a gelatinous mucoid mass, thatkeep the eggs safe from breaking due to water currents while they arefertilized externally by the male (Sawaya, 1964). Once the eggs are fertilized,the mucoid mass collapses leaving the eggs into the sea water (Mandal, 2012). Since they have no yolky eggs, thehatching phase develops rapidly to a tornaria larva free swimming with cilia(Mertz 2004). After a determined number of days or weeks, a furrow is assembledaround the trunk larval and the anterior region is intended to convert into theproboscis (Mandal, 2012). The larvae settle down and thus, develop into a youngadult (Mandal, 2012).
Asexualreproduction is uncommon, but might occur in some acorn worms by fragmentationof the body in the adult phase (Mertz 2004)(figure 8).
Figure 8 - Reproduction cycle of a Balanoglossus sp (Dakuhippo, 2011)
Cleavageis radial, holoblastic and equal;gastrulation occurs by invagination and blastopore origins the anus (Marques, undated). |